In general, fastening members having various sizes and shapes for securely fixing or connecting parts are used in mechanical devices or various structures. Such fastening members are fastened and unfastened by means of a spanner or a wrench.
As shown in FIG. 1, the spanner or the wrench 100 includes a handle 110 having a predetermined length, and a pair of opposed clamping parts 120 formed at both ends thereof to clamp and unclamp a fastening member 200 such as a bolt or a nut.
The wrench 100 includes a knurled handle 110 that has a predetermined length to allow an operator to grasp the handle 110 and is provided with multiple protrusions and multiple recesses alternately arranged with each other in the transverse and longitudinal directions. In addition, the wrench 100 includes a pair of opposed clamping parts 120 formed at both ends of the handle 110 to correspond to the fastening member 200 of a square or hexagonal shape. In other words, each of the clamping parts 120 is formed in a square or hexagonal shape so that the nut or the bolt head is fitted into a jaw opening of the clamping part 120, and is manufactured into various sizes so that the clamping part 120 is used to fasten and unfasten the fastening members 200 of various sizes.
The above-mentioned wrench 100 is configured such that an operator places the clamping part 120 on the bolt head or the nut of a square or hexagonal shape and rotates the clamping part 120 in one direction or in the reverse direction to achieve the fastening or unfastening operation.
However, the wrench 100 entails a problem in that since it is used only for a single kind of the fastening member 200 having a given size, the operator suffers from an inconvenience of having to prepare the wrenches 100 having various sizes to fit the fastening members 200 of various sizes.
In addition, the wrench 100 can be applied only to the fastening member 200 such as a bolt and a nut, and a separate tool is necessary to fasten and unfasten a mechanical element such as a pipe.
In an attempt to solve the above problems, patent document 1 has proposed an adjustable universal pipe fastening tool configured to fasten and unfasten mechanical elements having various sizes and shapes. As shown in FIG. 2, in a polygonal dimension conversion wrench proposed in the patent document 1 as an example of the adjustable universal pipe fastening tool, concaved recesses 4 are formed in a clamping part 2 of a main body 1, fixing pins 5 capable of attaching a folded plate 3 are elastically mounted in the concaved recesses 4, and leg portions 3′ of the folded plates 3 are fitted into the concaved recesses 4 to cause depressed portions 3″ of the leg portions 3′ to be fixed by the fixing pins 5 so that the dimension of the clamping part 2 is changed by the thickness of the folded part 3, and thereby implementing a general purpose wrench enabling a free change in the dimension through the use of the folded plates of various thicknesses as well as a polygonal dimension conversion wrench enabling the creation of various dimensions through the use of polygonal dimension converting folded plates 6′ having different inner diameters.
However, the above-mentioned wrench encounter problems in that it must be provided with a plurality of folded plates, and the use of the wrench may be restricted due to a loss of the folded plates.